NI Lock in amplifier

[Coq_Rouge]

I do not think it is a good idea. A lock in amp, requires simultaneous sampling. Your Daq unit is not such a device. Another question. Do you need a full Lock in amp, or just a phase sensitive detector.   

[umadevi]

thnks for your replay.i want  to lock the laser at 780nm.(This laser is External Cavity Diode Laser).Why it is not possible? here i decided to take the photodetector  output  throgh daq  , this output is multiplied with sinwave ..  and then pass through low pass filter. SO ITS OUTPUT IS DC.. i will get tis output through daq.and then it connected to ECDL.. this is my plan is it possible?

[Coq_Rouge]

So you do not need the "lock in" part of a lock in amplifier? A lock-in usually measures both in-phase (X) and out-of-phase (Y) components of the signal and can calculate the magnitude (R) from that. Do you need both the X, and Y components